#include <bits/stdc++.h>

using namespace std;

class Solution
{
public:
    int longestPalindromeSubseq(string s)
    {
        int length = s.size();
        vector<vector<int>> dp(s.size(), vector<int>(s.size(), 0));
        for (int i = length - 1; i >= 0; i--)
        {
            for (int j = i; j < length; j++)
            {
                if (s[i] == s[j])
                {
                    if (i == j)
                    {
                        dp[i][j] = 1;
                    }
                    else
                    {
                        dp[i][j] = dp[i + 1][j - 1] + 2;
                    }
                }
                else
                {
                    dp[i][j] = max(dp[i][j - 1], dp[i + 1][j]);
                }
            }
        }
        return dp[0][length - 1];
    }
};

int main()
{
    string s{"bbbab"};
    Solution sol;
    cout << sol.longestPalindromeSubseq(s) << endl;
    return 0;
}